Ganging electrokinetic pumps

ABSTRACT

An electrokinetic system includes a first electrokinetic pump, a second electrokinetic pump, a reservoir having delivery fluid therein, and a controller. The first electrokinetic pump is configured to provide a first range of flow rates. The second electrokinetic pump is configured to provide a second range of flow rates. The second range includes flow rates that are greater than the flow rates of the first range. The reservoir is fluidically attached to the first electrokinetic pump and the second electrokinetic pump. The controller is configured to apply voltage to one of the first or second electrokinetic pumps and then apply voltage to the other of the first or second electrokinetic pumps so as to vary the flow rate range of delivery fluid pump from the reservoir.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No. 61/482,949, filed May 5, 2011, and titled “GANGING ELECTROKINETIC PUMPS,” which is herein incorporated by reference in its entirety.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.

FIELD

This application relates generally to methods for delivery a volume of fluid with a pump system. More specifically, the disclosure relates to a pump system including a plurality of electrokinetic pumps ganged together.

BACKGROUND

Electrokinetic (“EK”) or electro-osmotic manipulations of fluids represent the state-of-the art in controlled, high precision, small volume fluid transport and handling. Electro-osmosis involves the application of an electric potential to an electrolyte, in contact with a dielectric surface, to produce a net flow of the electrolyte.

EK pumps have widespread and wide ranging applications, such as for chemical analysis, drug delivery, and analyte sampling. However, there are several design challenges associated with using EK pumps, such as obtaining a high flow rate, a large range of flow rates from a single EK pump system, and achieving continuous flow.

Accordingly, the present disclosure is directed to a pump system having a plurality of EK pumps ganged together to achieve a high flow rates, a large range of flow rates, and/or substantially continuous flow.

SUMMARY OF THE DISCLOSURE

In general, in one aspect, an electrokinetic system includes a first electrokinetic pump, a second electrokinetic pump, a reservoir having delivery fluid therein, and a controller. The first electrokinetic pump is configured to provide a first range of flow rates. The second electrokinetic pump is configured to provide a second range of flow rates. The second range includes flow rates that are greater than the flow rates of the first range. The reservoir is fluidically attached to the first electrokinetic pump and the second electrokinetic pump. The controller is configured to apply voltage to one of the first or second electrokinetic pumps and then apply voltage to the other of the first or second electrokinetic pumps so as to vary the flow rate range of delivery fluid pump from the reservoir.

In general, in one aspect, a method of pumping fluid includes applying voltage with a controller to a first electrokinetic pump to pump delivery fluid from a reservoir at a first flow rate; and applying voltage with the controller to a second electrokinetic pump to pump delivery fluid from the reservoir at a second flow rate, the second flow rate different than the first flow rate.

These and other embodiments can include one or more of the following features. The flow rate range of the electrokinetic system can be from approximately 0.0001 mL/hr to 1,200 mL/hr, such as 0.0001 mL/hr to 1,000 mL/hr, for example 0.01 mL/hr to 30 mL/hr. The system can further include a third electrokinetic pump configured to provide a third range of flow rates. The third range can include flow rates that are greater than the flow rates of the second range. The reservoir can be fluidically connected to the third electrokinetic pump, and wherein the controller is configured to apply voltage to one of the first or second or third electrokinetic pumps and then apply voltage to the another of the first or second electrokinetic pumps so as to vary the flow rate range of delivery fluid pumped from the reservoir. The flow range of the first electrokinetic pump can be approximately 0.01-5 mL/hr, and the flow rate of second electrokinetic pump can be approximately 0.1-15 mL/hr. The first and second pumps can be electrically connected in parallel. The first electrokinetic pump can include a first pressure sensor, and the second electrokinetic pump can include a second pressure sensor. The first electrokinetic pump can include a first check valve, and the second electrokinetic pump can include a second check valve. The controller can be configured to apply voltage to both of the first and second electrokinetic pumps simultaneously to increase the flow rate of delivery fluid pumped from the reservoir.

In general, in one aspect, an electrokinetic system includes a first electrokinetic pump and a second electrokinetic pump, a reservoir having delivery fluid therein, and a controller. The reservoir is fluidically attached to the first electrokinetic pump and the second electrokinetic pump. The controller is configured to apply voltage in a first cycle to the first electrokinetic pump and to apply voltage in a second cycle to a second electrokinetic pump. The controller is further configured to stagger the start-time of the first and second cycles so as to provide substantially continuous flow of the delivery fluid from the reservoir.

In general, in one aspect, a method of pumping includes applying voltage in a first cycle to a first electrokinetic pump and applying voltage in a second cycle to a second pump. The first and second electrokintic pumps are fluidically connected to a reservoir having a delivery fluid therein. The start-time of the second cycle is delayed relative to the start-time of the first cycle so as to provide substantially continuous flow of the delivery fluid from the reservoir.

These and other embodiments can include one or more of the following features. The system can further include a third electrokinetic pump and a fourth electrokinetic pump. The reservoir can be fluidically attached to the third and fourth electrokinetic pumps. The controller can be configured to apply voltage in a third cycle to the third electrokinetic pump and to apply voltage in a fourth cycle to the fourth electrokinetic pump. The controller can be configured to stagger the start-times of the first, second, third, and fourth cycles so as to provide substantially continuous flow of the delivery fluid from the reservoir. The controller can be configured to synchronize the cycles such that the first cycle includes an intake or outtake stroke only when the second cycle includes a zero-voltage phase, the second cycle includes an intake or an outtake stroke only when the first cycle includes a zero-voltage phase, the third cycle includes an intake or an outtake stroke only when the fourth cycle includes a zero-voltage phase, the fourth cycle includes an intake or an outtake stroke only when the third cycle includes a zero-voltage phase. The controller can be further configured to synchronize the cycles such that the first cycle includes an intake stroke when the third cycle includes an outtake stroke, and the third cycle includes an intake stroke when the first cycle includes an outtake stroke. The controller can be configured to synchronize the cycles such that the first cycle includes an intake stroke while the second cycle includes an intake stroke. The third cycle can include an intake stroke while the second cycle includes an intake stroke. The fourth cycle can include an intake stroke while the third cycle includes an intake stroke. The first electrokinetic pump can be connected to a first electrokinetic engine, and the first electrokinetic engine can be further connected to a third electrokinetic pump. The second electrokinetic pump can be connected to a second electrokinetic engine, and the second electrokinetic engine can be further connected to a fourth electrokinetic pump. The first and second engines can be reciprocating engines. The instantaneous flow rate can never drop to zero during the delivery of fluid. The instantaneous flow rate of the system can vary by less than 20% from a target flow rate, such as less than 10%, for example less than 5%.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity in the claims that follow. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which:

FIG. 1 is a cross-sectional diagram of an EK pump assembly.

FIG. 2A shows an exemplary graph of voltage vs. time for an EK pump assembly. FIG. 2B shows the corresponding flow rate profile vs. time.

FIG. 3 shows a schematic of a ganged EK pump system having a plurality of EK pump assemblies connected together.

FIG. 4 shows a schematic a ganged EK pump system having two EK pump assemblies connected hydrodynamically and electrically in parallel.

FIG. 5A shows an exemplary graph of voltage vs. time for the ganged EK pump system of FIG. 4. FIG. 5B shows the corresponding flow rate profile vs. time.

FIG. 6 shows a schematic of a ganged EK pump system having two EK pump assemblies connected hydrodynamically in parallel and controlled by a single controller.

FIG. 7A shows an exemplary graph of voltage vs. time for the ganged EK pump system as shown in FIG. 6. FIG. 7B shows the corresponding flow rate profile vs. time.

FIG. 8 shows a schematic of a ganged EK pump system having two EK pump assemblies connected hydrodynamically in parallel and having distributed control.

FIG. 9A shows an exemplary graph of voltage vs. time for a ganged EK pump system having four EK pump assemblies connected as shown in FIG. 8 with no overlap in application of voltage. FIG. 9B shows the corresponding flow rate profile vs. time.

FIG. 10A shows an exemplary graph of voltage vs. time for a ganged EK pump system having four EK pump assemblies connected as shown in FIG. 8 with overlap in application of voltage. FIG. 10B shows the corresponding flow rate profile vs. time.

FIG. 11 shows a schematic of a ganged EK pump system having two reciprocating EK engines configured to run four electrokinetic pumps that are connected together hydrodynamically in parallel.

FIG. 12A shows an exemplary graph of voltage vs. time for the ganged EK pump system of FIG. 11 with no overlap in application of voltage. FIG. 12B shows the corresponding flow rate profile vs. time.

DETAILED DESCRIPTION

Certain specific details are set forth in the following description and figures to provide an understanding of various embodiments of the invention. Certain well-known details, associated electronics and devices are not set forth in the following disclosure to avoid unnecessarily obscuring the various embodiments of the invention. Further, those of ordinary skill in the relevant art will understand that they can practice other embodiments of the invention without one or more of the details described below. Finally, while various processes are described with reference to steps and sequences in the following disclosure, the description is for providing a clear implementation of particular embodiments of the invention, and the steps and sequences of steps should not be taken as required to practice this invention.

Referring to FIG. 1, an electrokinetic (“EK”) pump assembly 100 includes an EK pump 101 connected to an EK engine 103. The EK engine 103 includes a first chamber 102 and a second chamber 104 separated by a porous dielectric material 106, which provides a fluidic path between the first chamber 102 and the second chamber 104. Capacitive electrodes 108 a and 108 b are disposed within the first and second chambers 102, 104, respectively, and are situated adjacent to or near each side of the porous dielectric material 106. The EK engine 103 includes a movable member 110 in the first chamber 102, opposite the electrode 108 a. The moveable member 110 can be, for example, a flexible impermeable diaphragm. A pump fluid (or “engine fluid”), such as an electrolyte, can fill the EK engine, such as be present in the first and/or second chambers 102 and 104, including the space between the porous dielectric material 106 and the capacitive electrodes 108 a and 108 b. The capacitive electrodes 108 a and 108 b are in communication with an external voltage source, such as through lead wires or other conductive media.

The EK pump 101 includes a delivery chamber 122 and a movable member 113 having a first edge 112 contacting the delivery chamber 122 and a second edge 111 contacting the second chamber 104. In some embodiments, the first and second edges 112, 111 are flexible diaphragms having a mechanical piston therebetween. In other embodiments, the first and second edges 112, 111 are flexible diaphragms having a gel material therebetween. Gel couplings are described further in U.S. Provisional Patent Application No. 61/482,889, filed May 5, 2011, and titled “GEL COUPLING FOR ELECTROKINETIC DELIVERY SYSTEMS,” and U.S. patent application Ser. No. ______, filed herewith, and titled “GEL COUPLING FOR ELECTROKINETIC DELIVERY SYSTEMS,” the contents of both of which are incorporated herein by reference. In other embodiments, the first and second edges 112, 111 are edges of a single flexible member or diaphragm.

The delivery chamber 122 can include a delivery fluid, such as a drug or medication, e.g., insulin or pain management medications, or a cleansing fluid, such as a wound cleansing fluid, supplied to the delivery chamber 122 from a fluid reservoir 141. An inlet check valve 142 between the fluid reservoir 141 and delivery chamber 122 can control the supply of delivery fluid to the delivery chamber 122, while an outlet check valve 144 can control the delivery of delivery fluid from the delivery chamber 122, such as to a patient. A first pressure sensor 152 and a second pressure sensor 154 can monitor the flow of fluid from the system. Further, a flow restrictor 160 can be present in the pump 101 to produce a pressure differential between sensors 152, 154 so as to provide a mechanism for measuring the flow of the fluid. Mechanisms for monitoring fluid flow are described further in U.S. Provisional Patent Application No. 61/482,960, filed May 5, 2011, and titled “SYSTEM AND METHOD OF DIFFERENTIAL PRESSURE CONTROL OF A RCIPROCATING ELECTROKINETIC PUMP,” and U.S. patent application Ser. No. ______, filed herewith, and titled “SYSTEM AND METHOD OF DIFFERENTIAL PRESSURE CONTROL OF A RCIPROCATING ELECTROKINETIC PUMP.”

In use, the electrokinetic assembly 100 works by producing electrokinetic or electroostmostic flow. A voltage, such as a positive voltage, is applied to the electrodes 108 a, 108 b, which causes the engine fluid to move from the second chamber 104 to the first chamber 102. The engine fluid may flow through or around the electrodes 108 a and 108 b when moving between the chambers 104, 102. The flow of fluid causes the movable member 110 to be pushed out of the chamber 102 and the movable member 113 to be pulled into chamber 104. As a result of the movement of the movable member 113, delivery fluid is pulled from the reservoir 141 into the delivery chamber 122. The movement of delivery fluid from the reservoir into the delivery chamber 122 is called the “intake stroke” of the pump cycle. When the opposite voltage is applied, such as a negative voltage, fluid moves from the first chamber 102 to the second chamber 104. The movement of engine fluid between chambers causes the movable member 110 to be pulled into the first chamber 102 and the movable member 113 to expand to compensate for the additional volume of engine fluid in the second chamber 104. As a result, delivery fluid in the chamber 122 is pushed out of the chamber 122 and delivered, such as to a patient, through the outlet check valve 144. The delivery of fluid is called the “outtake stroke” of the pump cycle. Although the exemplary assemblies and systems described below are configured such that a positive voltage corresponds to the intake stroke and a negative voltage corresponds to an outtake stroke, it is to be understood that the opposite configuration is also possible—i.e., that a negative voltage corresponds to an intake stroke and a positive voltage corresponds to an outtake stroke. A controller can be used to control the voltage applied to the electrodes 108 a, 108 b.

Referring to FIGS. 1 and 2A, a controller can be configured to apply voltage to the EK assembly 100 in a pump cycle 261. Each pump cycle 261 includes an intake stroke 263, a dwell phase 265, an outtake stroke 267, and a wait phase 269. During the intake stroke 263, the controller applies a positive voltage to pull delivery fluid from the fluid reservoir 141 into the pump 101. Likewise, during the outtake stroke 267, a negative voltage is applied to push delivery fluid out of the pump 101, e.g., to a patient. During the dwell phase 265 and the wait phase 269, a zero voltage is applied. The zero voltage phases are important to allow for the delivery fluid to finish traveling through the pump 101 after the voltage has stopped being applied and to control the overall flow rate of the delivery fluid from the pump 101, i.e. to allow fluids in the various chambers to settle and to allow the check valves to fully close to prevent fluid back-flow into the pumping chamber. In some embodiments, the controller can have a programmed delay 271 prior to the start-time 273 of the cycle of cycles 261. Referring to FIGS. 2A and 2B, each pump cycle 261 will result in the delivery of a single bolus 275 of fluid.

The electrokinetic pump assembly 100 can be configured to stop pumping in a particular direction, i.e. with negative or positive current, prior to the occurrence of a Faradaic process in the liquid. Accordingly, the electrodes will advantageously not generate gas or significantly alter the pH of the pump fluid. The set-up and use of various EK pump assemblies are further described in U.S. Pat. Nos. 7,235,164 and 7,517,440, the contents of which are incorporated herein by reference.

Referring to FIG. 3, two or more EK pump assemblies 300 a, 300 b, 300 c, 300 d can be ganged, i.e., connected together, in a single electrokinetic pump system 399 to deliver fluid from a single reservoir 341. The pump assemblies 300 a, 300 b, 300 c, 300 d can have their output lines connected at a fitting 383, such as a T-fitting or trio of Y-fittings, so as to provide a single output 305. A controller 391 can be configured to control the cycles all of the pump systems 300 a, 300 b, 300 c, 300 d such that the desired flow profile is obtained from the EK pump system 399.

Referring to FIG. 4, two or more EK pump assemblies 400 a (having EK engine 403 a and EK pump 401 a), 400 b (having EK engine 403 b and EK pump 401 b) can be connected together in parallel both electrically and hydrodynamically to form a single EK pump system 499. A single controller 491 can be connected to both EK engines 403 a, 403 b to control delivery of fluid from a single reservoir 441. Because the sensors are connected in parallel, a single set of pressure sensors 452, 454 and a single set of check valves 442, 444 can be used for the entire EK pump system 499.

In use, referring to FIGS. 4 and 5A, when the controller 491 applies a positive voltage, both pump assemblies 400 a, 400 b will produce an intake stroke 563 a, 563 b, and when the controller 491 applies a negative voltage, both pump assemblies 400 a, 400 b will produce an outtake stroke 567 a, 567 b. The EK pump system 499 will experience a single dwell time 565 and a single wait time 569. As shown in FIG. 5B, the individual boluses 575 a, 575 b associated with each pump assembly 400 a, 400 b, respectfully, will occur at the same time, thereby producing a single large bolus 575 of fluid for the EK pump system 499.

Advantageously, by ganging pump assemblies in parallel as described with reference to FIGS. 4 and 5, the flow rate of the EK pump system can be increased without hindering manufacturability or efficiency. Because the flow rate of a single EK assembly is directly proportional to the area of the EK pump element, one mechanism for increasing the flow rate is to increase the size of the EK pump element. However, doing so can cause manufacturing difficulties, such as producing a large porous dielectric material and requiring production of a variety of sizes of EK engines. Another mechanism for increasing the flow rate is to increase the applied voltage. However, doing so can be inefficient because, while the voltage is directly proportional to the flow rate, increasing the voltage also increases the required current draw. That is, because power is equal to voltages times the current, increasing the voltage will increase the amount of power required by a higher percentage than the flow rate is increased. For example, if an engine produces a particular flow rate by drawing 30 mA of current at 3 volts (requiring a power of 90 mW), the flow rate can be increased seven times by increasing the voltage to 21 volts. Correspondingly, the engine's current draw will increase from 30 mA to 210 mA proportionally, and the required power will increase to 4,410 mW. This method of increase flow rate is inefficient because the pump system's power consumption has been increased 49 times, while the flow rate has only been increased seven times. Ganging EK assemblies together to increase the flow rate avoids both of these problems while still allowing for an increased flow rate. Moreover, ganging EK assemblies together in parallel can advantageously provide a safety check; if one pump assembly fails, the other pump assemblies can be used to compensate.

Referring to FIG. 6, two or more EK pump assemblies 600 a (having EK engine 603 a and EK pump 601 a), 600 b (having EK engine 603 b and EK pump 601 b) can be connected together in parallel hydrodynamically but remain electrically independent to form EK pump system 699. Each EK system 600 a, 600 b can include a separate intake valve 642 a, 642 b, outtake valve 644 a, 644 b, first pressure sensor 652 a, 652 b, and second pressure sensor 654 a, 654 b, respectively. A single controller 691 can be connected to both EK engines 603 a, 603 b to control delivery of fluid with the EK pump system 699 from a single reservoir 641. The controller 691 can be connected to a multiplexer or mechanical relay 693 to select which pump to communicate with at a given time.

EK assembly 600 a can have a different range of flow rates than EK assembly 600 b. For example, EK assembly 600 b can be configured to run at greater flow rates than EK assembly 600 a. Although FIG. 6 shows only two EK assemblies 600 a, 600 b connected together, there can be more than two EK assemblies in a ganged EK pump system. For example, a third EK system could be connected to the first and second pumps and configured to run at a range of flow rates different than the first or second ranges, such as a range having rates that are higher than the first and second EK systems. In some embodiments, at least one of the EK systems is configured to pump fluid at approximately 0.01 to 5 mL/hr and at least one of the EK systems is configured to pump fluid at approximately 0.1 to 15 mL/hr. In another embodiment, at least one of the EK systems is configured to pump fluid at approximately 0.01 to 5 mL/hr and at least on of the EK systems is configure to pump fluid at approximately 1 to 300 mL/hr. In another embodiment, at least one of the EK systems is configured to pump fluid at approximately 0.1 to 15 mL/hr and at least one of the EK systems is configured to pump fluid at approximately 1 to 300 mL/hr.

In use, referring to FIGS. 6 and 7A, the controller 691 can first apply a positive voltage to pump assembly 600 a to produce an intake stroke 763 a and then a negative voltage to produce an outtake stroke 767 a. Subsequently, the controller 691 can switch and apply a positive voltage to pump assembly 600 b to produce an intake stroke 763 b and then a negative voltage to produce an outtake stroke 767 b. Optionally, the controller 691 can then switch back to running EK pump system 600 a. As shown in FIG. 7B, the bolus 775 b produced by the second EK pump assembly 600 b, designed to have a higher flow rate than the first EK pump assembly 600 a, will be larger than the bolus 775 a produced by the fist EK pump assembly 600 a.

Advantageously, by ganging together pumps of different flow rate ranges in the configuration shown in FIG. 6, a system having a wide range of flow rates can be achieved. For example, the system can be configured to have a range of flow rates from 0.0001 mL/hr to 1200 mL/hr, such as 0.0001 mL/hr to 1,000 mL/hr, for example 0.01 mL/hr to 30 mL/hr. Having a wide range of flow rates can be advantageous during various medical procedures, such as IV infusion or insulin delivery. For example, during insulin delivery, basal flow rates need to be very low, such as 0.1 ml/hr, while bolus rates need to be very fast, such as 30 ml/hr.

Moreover, in some embodiments, the controller 691 can run both EK assemblies 600 a, 600 b at the same time, thereby increasing the total flow rate range achievable by the EK pump system 699. By ganging EK assemblies of different sizes together in a single EK pump system and running the pumps simultaneously, the accuracy of the system can be increased relative to using a single EK assembly having a large flow rate. That is, each EK pump system has an optimal delivery volume where the EK engine is most efficient. For example, a large delivery pump that has only a small percentage error can still cause significant errors if being used to deliver small volumes. Moreover, often the corresponding system components, such as the sensors and check valves, can be dialed with a resolution that matches the optimal volume to achieve better accuracy. Further, timing errors caused by slow responsiveness of larger components can be minimized by controlling smaller pumps to move small amounts of liquid rather than using a large pump to deliver small volumes of liquid. Accordingly, a ganged pumped system having pumps of different volumes can advantageously provide a more robust response range based upon the optimal ranges of the pumps used.

Referring to FIG. 8, two or more EK pump assemblies 800 a (having EK engine 803 a and EK pump 801 a), 800 b (having EK engine 803 b and EK pump 801 b) can be connected together hydrodynamically in parallel with distributed control to form an EK pump system 899. Thus, each EK assembly 800 a, 800 b can include a separate intake valve 842 a, 842 b, outtake valve 844 a, 844 b, first pressure sensor 852 a, 852 b, and second pressure sensor 854 a, 854 b, respectively. A single master controller 891 can be used for the EK pump system 899. The master controller 891 can be connected to a first slave controller 895 a for controlling delivery of fluid from the reservoir 841 with the first EK assembly 800 a and to a second slave controller 895 b for controlling delivery of fluid from the reservoir 841 with the second EK assembly 800 b.

The slave controllers 895 a, 895 b can, for example, perform feedback measurements, control loop calculations, and current controls. The master controller 891, in contrast, can be configured to align the pump cycles of each of the assemblies 800 a, 800 b to achieve the desired flow profile for the EK pump system 899. Communication between the master controller 891 and slave controllers 895 a, 895 b can include which slave is controlling delivery at a particular time, what volume of fluid is delivered, and any errors in delivery.

In use, referring to FIGS. 8, 9A, and 10A (four connected EK systems are shown in the graphs of FIGS. 9A and 10A), the controller 891 can be configured to synchronize the pump cycles of each of the EK assemblies 800 to achieve substantially continuous flow for the EK pump system 899.

In one embodiment, shown in FIG. 9A, the controller 891 can be configured to stagger the start-times 973 a, 973 b, 973 c, 973 d such that there is no overlap between any of the intake strokes 963 a, 963 b, 963 c, 963 d and so that there is no overlap between the outtake strokes 967 a, 967 b, 967 c, 967 d. Thus, for example, the cycle for the first pump assembly can start at time zero, the cycle for the second pump assembly can start after a delay 971 b, which corresponds to the length of time of the intake stroke 963 a, the cycle for the third pump assembly can start after a delay 971 c, which corresponds to the length of time required for the intake strokes 963 a and 963 b, and the cycle for the fourth pump assembly can start after a delay 971 d, which corresponds to the length of time required for the intake strokes 963 a, 963 b, 963 c. Accordingly, as shown in FIG. 9B, there will be a series of boluses 975 a, 975 b, 975 c, 975 d strung closely together so as to achieve substantially continuous flow of fluid, i.e. the instantaneous flow rate measured at the distal end of the pump system proximate to where the pump system is connected to the patient never drops to zero.

In another embodiment, shown in FIG. 10A, the controller 891 can be configured to stagger the start-times 1073 a, 1073 b, 1073 c, 1073 d such that there is overlap between at least some of the intake strokes 1063 a, 1063 b, 1063 c, 1063 d and so that there is overlap between at least some of the outtake strokes 1067 a, 1067 b, 1067 c, 1067 d. Thus, for example, as shown in FIG. 10A, the cycle for the first pump assembly can start at time zero, the cycle for the second pump assembly can start after a delay 1071 b, which is shorter than the length of time of the intake stroke 1063 a, the cycle for the third pump assembly can start after a delay 1071 c, which has a length of time shorter than the length of delay 1071 b plus the intake stroke 1063 b, and the cycle for the fourth pump assembly can start after a delay 1071 d, which has a length of time shorter than the length of delay 1071 c plus the length of the intake stroke 1063 c. Accordingly, as shown in FIG. 10B, at least some of the boluses 1075 a, 1075 b, 1075 c, 1075 d will overlap to achieve substantially continuous flow.

In some embodiments, the controller 891 can run two or more cycles concurrently so as to increase flow.

Advantageously, the system set-up of FIGS. 8, 9, and 10 can provide substantially continuous flow of fluid from the fluid reservoir. Substantially continuous flow can advantageously help minimize the peak concentration level of delivery fluid, such as a medication, given to a patient compared to a standard bolus or injection. Minimizing peak concentration level can reduce the risk of toxic effects associated with peak concentrations. Such a system can be particularly advantageous for medications having a high toxicity.

Further, by including overlapping boluses as described above with respect to FIGS. 10A and 10B, the variation in the instantaneous flow rate can advantageously be decreased. For example, the instantaneous flow rate measured at the distal end of the pump will never drop to zero and can be maintained within 20% of the target flow rate, such as within 10% of the target flow rate, for example within 5% of the target flow rate.

Referring to FIG. 11, two or more EK pump assemblies 1100 a, 1100 b can be connected together in EK pump system 1199. The system 1199 can have the same features as the system of FIG. 8 except that each EK pump assembly 1100 a, 1100 b can include reciprocating engines 1103 a, 1103 b. Accordingly, engine 1103 a can power two pumps 1101 a, 1101 c, and engine 1103 b can power two pumps 1101 b, 1101 d. Further, each pump can have its own set of pressure sensors and inlet/outlet valves.

Referring to FIGS. 11 and 12A, EK engine 1103 a can produce an intake stroke 1263 a and an outtake stroke 1267 c at the same time. Further, EK engine 1103 b can produce an intake stroke 1263 b and an outtake stroke 1267 d at the same time. Accordingly, only one delay 1271 b is needed to synchronize the EK pump assemblies 1100 a, 1100 b, resulting in boluses 1275 a, 1275 b, 1275 c, 1275 d that produce substantially continuous flow. Advantageously, reciprocating pumps can be cheaper and easier to assemble, are more compact, and can increase the efficiency of the system relative to single engine—single pump systems. Moreover, although FIG. 12A shows only non-overlapping intake and outtake strokes, the controller 1191 can be configured to overlap the intake/outtake strokes so as to achieve more continuous flow for the EK pump system 1199.

As for additional details pertinent to the present invention, materials and manufacturing techniques may be employed as within the level of those with skill in the relevant art. The same may hold true with respect to method-based aspects of the invention in terms of additional acts commonly or logically employed. Also, it is contemplated that any optional feature of the inventive variations described may be set forth and claimed independently, or in combination with any one or more of the features described herein. Likewise, reference to a singular item, includes the possibility that there are plural of the same items present. More specifically, as used herein and in the appended claims, the singular forms “a,” “and,” “said,” and “the” include plural referents unless the context clearly dictates otherwise. It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as “solely,” “only” and the like in connection with the recitation of claim elements, or use of a “negative” limitation. Unless defined otherwise herein, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The breadth of the present invention is not to be limited by the subject specification, but rather only by the plain meaning of the claim terms employed. 

1. An electrokinetic pump system, comprising: a reservoir configured to have a delivery fluid therein; a first electrokinetic pump assembly fluidically connected to the reservoir and configured to pump the delivery fluid from the reservoir at a first range of flow rates; a second electrokinetic pump assembly fluidically connected to the reservoir and configured to pump the delivery fluid from the reservoir at a second range of flow rates, the second range including flow rates that are greater than the flow rates of the first range; and a controller configured to apply voltage to one of the first or second electrokinetic pump assemblies and then apply voltage to the other of the first or second electrokinetic pump assemblies so as to vary the flow rate of delivery fluid pumped by the electrokinetic pump system.
 2. The electrokinetic pump system of claim 1, wherein a total flow rate range of the system is between approximately 0.0001 ml/hr and 1,200 ml/hr.
 3. The electrokinetic pump system of claim 2, wherein the total flow rate range of the system is between approximately 0.0001 ml/hr and 1,000 ml/hr.
 4. The electrokinetic pump system of claim 3, wherein the total flow rate range of the system is between approximately 0.01 ml/hr and 30 ml/hr.
 5. The electrokinetic system of claim 1, further comprising a third electrokinetic pump assembly fluidically connected to the reservoir and configured to provide a third range of flow rates, the third range of flow rates including flow rates that are greater than the flow rates of the second range, wherein the controller is configured to apply voltage to one of the first or second or third electrokinetic pump assemblies and then apply voltage to the another of the first or second electrokinetic pump assemblies so as to vary the flow rate of delivery fluid pumped by the electrokinetic pump system.
 6. The electrokinetic system of claim 1, wherein the flow rate range of the first electrokinetic pump assembly is between approximately 0.01 and 5 ml/hr and the flow rate range of the second electrokinetic pump assembly is between approximately 0.1 ml/hr and 15 ml/hr.
 7. The electrokinetic system of claim 1, wherein the first and second pump assemblies are electrically connected in parallel.
 8. The electrokinetic system of claim 1, wherein the first electrokinetic pump assembly includes a first pressure sensor configured to detect a flow rate of delivery fluid pumped with the first electrokinetic pump assembly, and wherein the second electrokinetic pump assembly includes a second pressure sensor configured to detect a flow rate of delivery fluid pumped with the second electrokinetic pump assembly.
 9. The electrokinetic system of claim 1, wherein the first electrokinetic pump assembly includes a first check valve to control the flow rate of delivery fluid pumped from the first electrokinetic pump assembly, and wherein the second electrokinetic pump assembly includes a second check valve configured to control the flow rate of delivery fluid pumped from the second electrokinetic pump assembly.
 10. The electrokinetic system of claim 1, wherein the controller is further configured to apply voltage to both of the first and second electrokinetic pump assemblies simultaneously to increase the flow rate of delivery fluid pumped by the electrokinetic pump system.
 11. A method of pumping fluid in an electrokinetic pump system, comprising: applying voltage with a controller to a first electrokinetic pump assembly to pump delivery fluid from a reservoir at a first flow rate; and applying voltage with the controller to a second electrokinetic pump assembly to pump delivery fluid from the reservoir at a second flow rate, the second flow rate different than the first flow rate.
 12. The method of claim 11, wherein a total flow rate range of the electrokinetic pump system is between approximately 0.0001 ml/hr and 1,200 ml/hr.
 13. The method of claim 12, wherein the total flow rate range of the electrokinetic pump system is between approximately 0.0001 ml/hr and 1,000 ml/hr.
 14. The method of claim 13, wherein the total flow rate range of the electrokinetic pump system is between approximately 0.01 ml/hr to 30 ml/hr.
 15. The method of claim 11, further comprising applying voltage with the controller to a third electrokinetic pump assembly to pump delivery fluid from the reservoir at a third flow rate, the third flow rate different than the first and second flow rates.
 16. The method of claim 11, wherein a flow rate range of the first electrokinetic pump assembly is between approximately 0.01 ml/hr and 5 ml/hr, and wherein a flow rate range of the second electrokinetic pump assembly is between approximately 0.1 ml/hr and 15 ml/hr.
 17. The method of claim 11, wherein the first and second electrokinetic pump assemblies are electrically connected in parallel.
 18. The method of claim 11, further comprising measuring the flow rate of delivery fluid pumped by the first electrokinetic pump assembly with a first pressure sensor and measuring the flow rate of delivery fluid pumped by the second electrokinetic pump assembly with a second pressure sensor.
 19. The method of claim 11, further comprising controlling the flow of delivery fluid pumped by the first electrokinetic pump assembly with a first check valve and controlling the flow of delivery fluid pumped by the second electrokinetic pump assembly with a second check valve.
 20. The method of claim 11, wherein the voltage is applied with the controller to the first and second electrokinetic pump assemblies simultaneously to increase the flow rate of delivery fluid pumped by the electrokinetic pump system.
 21. An electrokinetic pump system comprising: a reservoir configured to have a delivery fluid therein; a first electrokinetic pump assembly fluidically connected to the reservoir and configured to pump the delivery fluid from the reservoir; a second electrokinetic pump assembly fluidically connected to the reservoir and configured to pump the delivery fluid from the reservoir; and a controller configured to apply voltage in a first cycle to the first electrokinetic pump assembly and to apply voltage in a second cycle to a second electrokinetic pump assembly, the controller configured to stagger the start-time of the first and second cycles so as to provide substantially continuous flow of the delivery fluid from the electrokinetic pump system.
 22. The electrokinetic pump system of claim 21, further comprising a third electrokinetic pump and a fourth electrokinetic pump, wherein the reservoir is fluidically attached to the third and fourth electrokinetic pumps, and wherein the controller is configured to apply voltage in a third cycle to the third electrokinetic pump and to apply voltage in a fourth cycle to the fourth electrokinetic pump, the controller configured to stagger the start-times of the first, second, third, and fourth cycles so as to provide substantially continuous flow of the delivery fluid pumped from the electrokinetic pump system.
 23. The electrokinetic pump system of claim 22, wherein the controller is configured to synchronize the cycles such that the first cycle includes an intake or outtake stroke only when the second cycle includes a zero-voltage phase, the second cycle includes an intake or an outtake stroke only when the first cycle includes a zero-voltage phase, the third cycle includes an intake or an outtake stroke only when the fourth cycle includes a zero-voltage phase, the fourth cycle includes an intake or an outtake stroke only when the third cycle includes a zero-voltage phase.
 24. The electrokinetic pump system of claim 23, wherein the controller is further configured to synchronize the cycles such that the first cycle includes an intake stroke when the third cycle includes an outtake stroke, and the third cycle includes an intake stroke when the first cycle includes an outtake stroke.
 25. The electrokinetic pump system of claim 21, wherein the controller is configured to synchronize the cycles such that the first cycle includes an intake stroke while the second cycle includes an intake stroke.
 26. The electrokinetic pump system of claim 25, wherein the third cycle includes an intake stroke while the second cycle includes an intake stroke.
 27. The electrokinetic pump system of claim 26, wherein the fourth cycle includes an intake stroke while the third cycle includes an intake stroke.
 28. The electrokinetic pump system of claim 21, wherein the first electrokinetic pump assembly includes a first electrokinetic engine and two electrokinetic pumps, and wherein the second electrokinetic pump assembly includes a second electrokinetic engine and two additional electrokinetic pumps, the first and second engines being reciprocating engines.
 29. The electrokinetic pump system of claim 1, wherein the controller is configured such that an instantaneous flow rate of the delivery fluid pumped from the electrokinetic pump system never drops to zero during pumping of the delivery fluid.
 30. The electrokinetic pump system of claim 21, wherein the controller is configured such that an instantaneous flow rate delivery fluid pumped from the electrokinetic pump system varies by less than 20% from a target flow rate.
 31. The electrokinetic pump system of claim 30, wherein the controller is configured such that the instantaneous flow rate varies by less than 10%.
 32. The electrokinetic pump system of claim 31, wherein the controller is configured such that the instantaneous flow rate varies by less than 5%.
 33. A method of pumping fluid with an electrokinetic pump system, comprising: applying voltage in a first cycle to a first electrokinetic pump assembly to pump delivery fluid from a reservoir with the first electrokinetic pump assembly; applying voltage in a second cycle to a second electrokinetic pump assembly to pump delivery fluid from the reservoir with the second electrokinetic pump assembly; wherein the start-time of the second cycle is delayed relative to the start-time of the first cycle so as to provide substantially continuous flow of the delivery fluid from the electrokinetic pump system.
 34. The method of claim 33, further comprising applying voltage in a third cycle to a third electrokinetic pump assembly to pump delivery fluid from the reservoir with the third electrokinetic pump assembly and applying voltage in a fourth cycle to a fourth electrokinetic pump assembly to pump delivery fluid from the reservoir with the fourth electrokinetic pump assembly, wherein the start-times of third and fourth cycles are delayed relative to the start-time of the first and second cycle so as to provide substantially continuous flow of the delivery fluid from the electrokinetic pump system.
 35. The method of claim 34, further comprising synchronizing the cycles such that the first cycle includes an intake or outtake stroke only when the second cycle includes a zero-voltage phase, the second cycle includes an intake or an outtake stroke only when the first cycle includes a zero-voltage phase, the third cycle includes an intake or an outtake stroke only when the fourth cycle includes a zero-voltage phase, the fourth cycle includes an intake or an outtake stroke only when the third cycle includes a zero-voltage phase.
 36. The method of claim 35, further comprising synchronizing the cycles such that the first cycle includes an intake stroke when the third cycle includes an outtake stroke, and the third cycle includes an intake stroke when the first cycle includes an outtake stroke.
 37. The method of claim 34, further comprising synchronizing the cycles such that the first cycle includes an intake stroke while the second cycle includes an intake stroke.
 38. The method of claim 37, further comprising synchronizing the cycles such that the third cycle includes an intake stroke while the second cycle includes an intake stroke.
 39. The method of claim 38, wherein the fourth cycle includes an intake stroke while the third cycle includes an intake stroke.
 40. The method of claim 33, wherein, when applying the voltage in the first cycle and the second cycle, an instantaneous flow rate of delivery fluid from the electrokinetic pump system never drops to zero.
 41. The method of claim 33, wherein applying the voltage in the first cycle and the second cycle causes variations in an instantaneous flow rate of the delivery fluid from the electrokinetic pump system of less than 20% from a target flow rate.
 42. The method of claim 41, wherein the instantaneous flow rate varies by less than 10%.
 43. The method of claim 42, wherein the instantaneous flow rate varies by less than 5%. 